1. Field of the Invention
This invention relates to a recording apparatus and/or a reproducing apparatus capable of recording and/or reproducing audio data, etc. for a disc-shaped recording medium, for example. More particularly, this invention relates to a memory control device equipped in these kinds of apparatus.
2. Description of the Prior Art
There have been known data rewritable magneto-optical discs on which a user can record music data, etc. The shockproof function of these discs can be improved by utilizing a buffer RAM.
In a reproducing operation, audio data read out from a magneto-optical disc is intermittently written into a buffer RAM at a high rate. Then this data is continuously read out from the buffer RAM at low rate while conducting a demodulation processing to obtain audio reproduction signals. In this way, a certain amount of data is accumulated in the buffer RAM at all times. Thus, the audio data can be continuously read out from the buffer RAM even when a track jump occurs due to external vibration or the like and the data read-out operation from the magneto-optical disc is temporarily interrupted, so that the reproduced signals can be output without interruption.
Further, in a recording operation, input data is continuously and temporarily written into the buffer RAM at a low rate. This data is then intermittently read out at a high rate and supplied to a recording head to perform a recording operation on the disc.
A recording track of the magneto-optical disc comprises continuously-formed clusters CL each of which includes a sub data area of 4 sectors and a main data area of 32 sectors as shown in FIG. 1. Each cluster comprises 36 sectors and each sector comprises 2352 bytes.
One cluster serves as a minimum unit for the recording operation. One cluster has the length corresponding to two or three rounds of the disc. An address is recorded for every sector. The sub data area of 4 sectors is used for sub data or as a linking area. TOC data, audio data, etc. are recorded in the main data area of 32 sectors.
The sector is further divided into sound groups. Two sectors are divided into 11 sound groups. The data are recorded in a sound group of 424 bytes while being separated into left and right channels. Each sound group contains audio data whose time corresponds to 11.6 msec. Further, 212 bytes which serve as a data area of Left-channel or Right-channel is called a "sound frame".
When the recording and/or reproducing operation is conducted through the buffer RAM on data which is recorded on the disc having the format described above, the buffer RAM carries out its storage operation on a sector basis. That is, a sector address and a byte address (0 to 2351 byte) in the sector are combined with each other to generate an access address. The write-in and read-out operations are carried out on the basis of this access address.
In magneto-optical systems according to the conventions described above, there is a system controller for controlling the whole processing of the magneto-optical system. It is preferable that various kinds of information for a read-out sector are obtained when the data of the sector is read out from the buffer RAM. For example, due to the data reproducing operation through the buffer RAM, a time lag occurs between the time when the data of a sector is read out from the disc and the time when it is actually reproduced. Thus, it is preferable that information relating to a music play progress time of the sector be read out at the time when the data of the sector is read out from the buffer RAM of the sector.
In addition, it is also very preferable that information such as a track number, track change information, track mode information on identification of stereo/monaural, emphasis, inhibition or permission of copyright, link information for front and rear sides in managing information of audio data, error information, etc. can be written in the buffer RAM at the same time when the data of the sector is written into the buffer RAM. It is also preferable that this information be read out at the same time when the data of the sector is read out from the buffer RAM. Hereinafter, these kinds of information which are stored in the buffer RAM along with the sector are referred to as "additive data".
Therefore, when the data of a sector is written into the buffer RAM, the above kinds of additive data are conventionally over-written on data portions which subsequently become unnecessary. These data portions which subsequently become unnecessary include a sync data (924h.about.92Fh), a mode data (003h), and a sub header (004h.about.007h) as in shown as FIG. 2 (Note that numerical values affixed with an "h" in the specification are in hexadecimal notation). These kinds of additive data are stored along with an associated sector in the buffer RAM.
However, an address indication is required for the read-out of the additive data, and thus the system controller is required to carry out management of addresses at which the additive data are written and read-out addresses for indicating processing. This increases the processing load of the system controller.